We propose to continue our studies of the interaction between the SV40 T-antigen and regulatory sequences on the viral genome. In particular, we have begun to investigate the mechanism of transcriptional autoregulation in SV40 in vitro by purified T-antigen. In addition, we are pursuing the molecular events that lead to A gene dependent viral DNA replication in permissive monkey cells. We are also isolating the T-antigen/53K cellular functions of the A gene in nonpermissive cells. Finally, we have devised a number of assays for characterizing the ATPase activity of T antigen by utilizing monoclonal antibodies to define the functional portion of the molecule.